In the recent years wind power has become a quite attractive source of renewable energy and many wind turbines have been built all over the world. This increases the demand for better maintenance and monitoring of wind turbine components. Nowadays there are three schemes for component maintenance: breakdown maintenance; preventive maintenance based on the average component lifetime; and predictive maintenance based on monitoring the health of a component. However, with respect to the predictive maintenance strategy, there are some component faults, for example related to blades and associated sensors that are difficult to diagnose by the known methods and techniques, faults that can lead to worsened efficiency or to overload and shortened lifetime of the blades. Such faults do not necessarily result in a rapid breakdown, but are often noticed after a period of time, e.g. when the average yearly energy production of a wind turbine differs from the expected production.
Furthermore, some defects can only be detected with existing methods, but the component giving rise to the defect cannot be isolated without human intervention.
Thus a new method and a system are needed for diagnosis of blades and associated components. This is in particular the case for a wind turbine blade and associated sensors.
In view of the present invention there will be given hereunder some definitions of the most used terms in this patent application. However, these term definitions should not be limiting to the present invention and any other appropriate and/or suitable term definition(s) should be possible to use.
The pitch angle θ is defined by the angle between the blade root chord and the rotor rotational plane. A pitch rotation is a rotation of the blade along its longitudinal axis.
The azimuth angle δ is defined by the angular position of the rotor as the (front view) clockwise or anticlockwise angle between current angular position of the blade, e.g. the first blade (blade No. 1, B1), and the vertical down.
The blade load is the torque experienced by the blade due to different forces acting on the whole or parts of the blade.
A pitch reference angle θref is the desired value of the pitch angle θ and an azimuth reference angle δref is the desired value of the azimuth angle δ.